The invention relates to solar fluid heating systems and more particularly to a solar fluid heating system of series cascade design for direct solar energy heating of fluids using total internal reflection to trap radiation in the fluid, thereby enhancing the absorption.
The energy situation in the United States and throughout the world is becoming extremely critical. Fossil fuels are in short supply and have become extremely expensive. The supply of oil is greatly affected by the frequently volatile world political situation. Nuclear power has reached a stalemate because of safety concerns and the waste disposal problem. Furthermore, nuclear fuel may soon be critically in short supply. Advanced technologies such as fusion energy cannot be developed soon enough to meet the current energy crisis. The United States has set a major policy goal of reducing energy consumption, particularly oil, in order to break the dependency on foreign supplies.
The sun is a universally available and abundant source of energy which is largely untapped. Advanced solar energy technology such as photovoltaic cells and large scale energy converters may require long-term development. However, solar fluid heating systems designed for individual homes can result in significant energy savings by being used to provide hot water or to heat swimming pools or even to heat the home. Many rooftop systems for gathering solar energy have already been developed.
U.S. Pat. No. 4,047,518 to Anderson shows a solar heating system in which heat is absorbed by a black material suspended in the liquid. The black heat absorbing liquid exchanges its heat content to another liquid through a heat exchanger.
U.S. Pat. No. 4,142,513 to Auger shows a solar heater with a gravity driven flow in which a fluid is heated between two black, thin films.
U.S. Pat. No. 3,991,742 to Gerber discloses a solar heating system in which a fluid is heated between two thin, flat plates, with a corrugated or mesh spreader being used to equalize the fluid flow.
U.S. Pat. No. 4,076,015 to Mattson shows a solar energy collector with a combination of reflecting and transmitting surfaces to increase collection efficiency.
U.S. Pat. No. 4,111,186 to Ross et al. shows a flat plat solar collector having a pack of plastic bubbles with the fluid circulating around the bubbles.
U.S. Pat. No. 4,019,496 to Cummings describes a solar collector having a plurality of fins which form radiation traps. The fins do not contact the fluid which circulates in pipes below the fins.
U.S. Pat. No. 4,154,220 to Loth describes a flat plate solar collector having fins for heating air which circulates around the fins. U.S. Pat. No. 4,079,724 to Zwillinger shows a solar collector with fins of complex geometry forming a radiation trap to heat gas that circulates between the fins or fluid that circulates in structural pipes supporting the fins.
Some disadvantages of the prior art are the complexity of the designs, with a corresponding high cost, and the lower efficiency, caused in part by the loss of incident energy at the absorbing surface because of reflections. The prior art does not provide a system whose performance can be optimized for a particular geographical location by the selection of a simple design parameter.
It is an object of the invention to provide a solar fluid heating system with enhanced collection efficiency over an extended range of geographical latitudes.
It is also an object of the invention to provide a solar fluid heating system with maximum heat absorption capability.
It is a further object of the invention to provide a solar fluid heating system in which radiation is trapped in the fluid to produce maximum heating.
It is also an object of the invention to provide a solar fluid heating system in which the maximum efficiency at a given latitude is independent of the angle at which the heating system is mounted or installed.
It is another object of the invention to provide a solar fluid heating system of simplified construction and low cost.
It is another object of the invention to provide a solar fluid heating system which can provide heated fluid through two independent flow systems.
Additional objects, novel features, and advantages will become apparent from the following specification with accompanying drawings, and appended claims.